Making sure I understand requirement 521.10.202

[dnb]

I have started to look at planning cable runs etc for the new house mainly so I can make sure all the services interfere with each other as little as possible. I've not done any wiring for a while (getting old!) so I looked at the new book and I noted a new rule saying that the wiring can't collapse prematurely if it is on fire. Here are two scenarios to aid my understanding: 

 

1. On the assumption that the cables are not "collapsing prematurely" when attached to large pieces of the house that are collapsing, is it still acceptable to run a new cable through holes in the neutral axis of a joist without additional support (providing all the other regs are satisfied, naturally)?

 

2. Conversely, if I counterbatten to provide a service void between the joists and plasterboard I should use some metal clips to support the cables on the sides of the counterbattens or joists in case the plasterboard fails for some reason, e.g covered in water from the melted plastic water pipe.

 

Or can I rely on plasterboard to not "collapse prematurely", so I don't need to bother? ( I don't really like this but I can't really explain why)

[Nickfromwales]

We use powder coated all round band routinely, more to keep the main trunk runs neat and tidy than to comply with regs, and mostly in new builds with pozi joists. 
Regs see a mechanically fixed ( screwed ) and plastered plasterboard as 30mins fire rated and also as a means of satisfying the arrest of falling cables. 
AFAIK the reg exists only fir surface mounted wiring ( where the “containment” is plastic trunking / conduit ) and then you must employ metal clips at X intervals, to reinforce the use of plastic ones in between, and in trunking you fit a metal C clip before the cables go in, mechanically fixed ( screwed etc ), and then the clip is bent to grip the bunched cables before fitting the lid on. 
To drill through the top or centre of joists complies, and even under-slinging in the counter batten space complies ( if boarded over / PB mechanically fixed ).
With pozi joists you can run through perpendicular and rely on the web spaces where the metal webs form a gusset to comply ( even if no PB is present ). 
The reg also only asks for this in areas deemed means of egress / escape, so can be filtered to suit. 
I prefer to see heavy ‘looms” banded regardless, and we fix all the bands at locations where the cables turn 90o or spur off from the main trunk runs, and again where we run parallel with the beams eg where noggins could suffice but the bands look neater, and then you are only dealing with one discipline too so easier than cutting and fitting timber IMO. 
For under-slinging as you suggest, I would just use plenty of the newer metal T/E clips to sleep easy. You’re going to have to clip so may as well use FR clips  

Edited October 7, 2020 by Nickfromwales

[Nickfromwales]

Just to add, the reg also covers cables run above false ( suspended ) ceilings. These are the biggest risk as folk just keep adding behind those Willy-nilly until you end up with a cross between a spider web and a birds nest !!